Studies suggest Medicare insurance has improved health outcomes for the elderly. However, what is unknown is whether the Medicare program, which provides near universal coverage for Americans over 65, may be rescuing those who lacked insurance while near-elderly or may be providing too little coverage too late for this group. Given that 25% of the near-elderly will experience a period without insurance, sorting out this relationship between health insurance and health in old age, could lead to important policy interventions to improve the health of the elderly. The principal aim of this project is to study whether these improvements ire more likely to occur among the elderly who were uninsured prior to qualifying for Medicare at age 65 or whether they occur equally among all Medicare beneficiaries. This study will inform whether a policy to extend Medicare to the near-elderly who have difficulty obtaining health insurance would improve their health trajectories into old age. Given that the Medicare program is facing insolvency and may have to consider raising the eligibility age to coincide with the increase in the eligibility age for Social Security, this study will also inform a policy of more immediate concern: how would changes in the age of eligibility for Medicare change health and medical service use of the elderly? The data source will be the Health and Retirement Study (HRS), which is an ongoing panel survey of a nationally representative cohort of 12,562 individuals who were 51-61 years old when the study started in 1992. Responses will be linked with their Medicare claims. A broad range of measures of health outcomes and medical service use will be evaluated. Before and after 65 changes in health trajectories and medical service use patterns will be estimated for the entire sample and for insurance status subgroups. Differences in these changes between groups will also be estimated. We will use these estimates to simulate the effect of changes in the age of Medicare eligibility on health, medical service use and Medicare expenditure.